I have good volume at low end of dial but the station 580 KC tunes quite broadly from about 550 to 580 (station is actually loudest at 560 KC). What would cause this? Am I overloading the annenna perhaps? Adjusting the padder doesn't seem to narrow the tuning.

Brian: the broadness is determined by the Q of the tuning ckt. I wouldn't expect the padder to improve that.

Does your set have an antenna trimmer? You might try adjusting that to reduce its capacity (and thus the signal strength).

If tuning is too sharp, that can cause loss of fidelity, since the outside edges of the sidebands can be clipped off. Broad tuning can reduce selectivity, but if you're not have a problem with that, then maybe you don't really have a problem?
Doug

:I have good volume at low end of dial but the station 580 KC tunes quite broadly from about 550 to 580 (station is actually loudest at 560 KC). What would cause this? Am I overloading the annenna perhaps? Adjusting the padder doesn't seem to narrow the tuning.

One other thought - you could try touching up the IF adjustments. That might sharpen the tuning.
Doug

The antenna trimmer would be the adjustment on the top of the antenna tuning gang portion?

:Brian: the broadness is determined by the Q of the tuning ckt. I wouldn't expect the padder to improve that.
:
:Does your set have an antenna trimmer? You might try adjusting that to reduce its capacity (and thus the signal strength).
:
:If tuning is too sharp, that can cause loss of fidelity, since the outside edges of the sidebands can be clipped off. Broad tuning can reduce selectivity, but if you're not have a problem with that, then maybe you don't really have a problem?
:Doug
:
::I have good volume at low end of dial but the station 580 KC tunes quite broadly from about 550 to 580 (station is actually loudest at 560 KC). What would cause this? Am I overloading the annenna perhaps? Adjusting the padder doesn't seem to narrow the tuning.

Brian - Normally not.

Can you link us to the schematic and/or model number?
Doug

:The antenna trimmer would be the adjustment on the top of the antenna tuning gang portion?
:
:
::Brian: the broadness is determined by the Q of the tuning ckt. I wouldn't expect the padder to improve that.
::
::Does your set have an antenna trimmer? You might try adjusting that to reduce its capacity (and thus the signal strength).
::
::If tuning is too sharp, that can cause loss of fidelity, since the outside edges of the sidebands can be clipped off. Broad tuning can reduce selectivity, but if you're not have a problem with that, then maybe you don't really have a problem?
::Doug
::
:::I have good volume at low end of dial but the station 580 KC tunes quite broadly from about 550 to 580 (station is actually loudest at 560 KC). What would cause this? Am I overloading the annenna perhaps? Adjusting the padder doesn't seem to narrow the tuning.

Can I send you the schematic via e-mail? It's not listed here, nor can I post it.

:Brian - Normally not.
:
:Can you link us to the schematic and/or model number?
:Doug
:
::The antenna trimmer would be the adjustment on the top of the antenna tuning gang portion?
::
::
:::Brian: the broadness is determined by the Q of the tuning ckt. I wouldn't expect the padder to improve that.
:::
:::Does your set have an antenna trimmer? You might try adjusting that to reduce its capacity (and thus the signal strength).
:::
:::If tuning is too sharp, that can cause loss of fidelity, since the outside edges of the sidebands can be clipped off. Broad tuning can reduce selectivity, but if you're not have a problem with that, then maybe you don't really have a problem?
:::Doug
:::
::::I have good volume at low end of dial but the station 580 KC tunes quite broadly from about 550 to 580 (station is actually loudest at 560 KC). What would cause this? Am I overloading the annenna perhaps? Adjusting the padder doesn't seem to narrow the tuning.

Just click on my name to send an email. Edit out "NO_SPAM" from the address.
Doug

:Can I send you the schematic via e-mail? It's not listed here, nor can I post it.
:

Hi

This may be normal? Stations on the low end of the dial are spaced out more than high end. Notice the spacing on the dial between 550 and 600. Compare that with 1400 to 1450. Low end is spread out.

Norm

:Just click on my name to send an email. Edit out "NO_SPAM" from the address.
:Doug
:
::Can I send you the schematic via e-mail? It's not listed here, nor can I post it.
::
:

Brian sent me his schematic. It's a Stewart-Warner, late '30s battery-powered supehet. Nothing remarkable that would suggest anything about his "problem".

Following up on Norm's post, the resonance freq for a parallel L-C tuning ckt is inversely proportional to the sqrt of the capacitance, C. (Not linearly related to C.)

Now, the problem is that as you tune to a lower freq (with a variable cap), that resonance formula causes the tuning to appear to spread out. (What's really happening is that as C in increased to tune a lower freq, the "effectiveness" per degree of rotation becomes lower.)

Some tuning caps have unsymmetric geometries to try to minimize this effect. But chances are, Brian's set has tuners that are symmetric about their axis.

I suggested to Brian that sharpening up the IF aligment might help a little. But otherwise, just live with it.

L-C resonance formula:

f = 1/(2pi sqrt LC)
Doug

:Hi
:
: This may be normal? Stations on the low end of the dial are spaced out more than high end. Notice the spacing on the dial between 550 and 600. Compare that with 1400 to 1450. Low end is spread out.
:
:Norm
:
:
::Just click on my name to send an email. Edit out "NO_SPAM" from the address.
::Doug
::
:::Can I send you the schematic via e-mail? It's not listed here, nor can I post it.
:::
::